Discovery and first experiments
DDoS are discovered and starts to be used by researchers and then script kiddies.
1996: Syn flood
1997-1998: smurf attacks and first DDoS tools come out
1999: Trinoo, Stacheldraht tools become popular
First DDoS big attacks
The experiments start to hit big targets which are usually unprepared to respond. Attackers feel very powerful.
2000: Attacks on ebay, yahoo, amazon, CNN
2002: Attack to the DNS root servers
2003: 1 milion zombie computers infected by the worm MyDoom perform a DDoS attack
DDoS against important targets
DDoS are used as a powerful tool to hit important targets and are used as a gun by cyber criminals.
Somone starts to speak about "cyber warfare".
2007: Cyber attacks against Estonia
2008: Cyber attacks against Georgia
2009: Attacks against UltraDNS, The Pirate Bay, Register.com
2009: Attacks against: South Korea, USA, Washington Post, New York Stock Exchange
2009: Attack against Iran
2009: Attacks against: Facebook, Twitter, Google
The Anonymous era
Hacktivism become popular, no one is safe. First attacks against critical infrastructures.
2010: Anonymous - Operation Payback
2011/2012: Operation Tunisia, Sony, Syria, MegaUpload, Russia, India, Japan, etc
2012/2013: Operation Ababil
2014: Operation HackingCup
2014: Attack against Feedly
2014: Bear malware targets US and Canadian critical infrastructure providers